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Popper’s three worlds and attitudes to the explanatory gap
New Ideas in Psychology 17 (1999) 31 — 39
Popper’s three worlds and attitudes to the explanatory gap Elizabeth Valentine* Department of Psychology, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
Abstract The thesis is explored that Popper’s three worlds may be used as an intuition pump to reveal the insight that all three attitudes to the explanatory gap (that there is no gap, an unclosable gap, or a closable gap) are true from different perspectives. Ontologically, there is only one world and no gap. Epistemically, there is an irresolvable duality, an unclosable gap. From the point of view of scientific theory, there is a soluble problem, that of providing a principled account of the relation between phenomenal features of consciousness and functional accounts in terms of behaviour, neurophysiology and physics. Requirements for filling the gap are examined in more detail, and attempts to fill the gap are discussed. It is argued that, on current knowledge, it appears that only at the level of sub-atomic physics can parallels with phenomenal features of consciousness be found that are sufficiently powerful to provide a transparent account. 1999 Elsevier Science Ltd. All rights reserved.
Since, therefore, the substance of the mind has been found to be extraordinarily mobile, it must consist of particles exceptionally small and smooth and round. - Lucretius.
1. The explanatory gap The central problem in the philosophy of mind, which has attracted more attention than any other, is that of the relation between phenomenal and functional consciousness, the mind—body or mind—brain problem, i.e., the relation between phenomenal experience (qualia, what it is like to be... a phrase due originally to Brian Farrell rather than Thomas Nagel) and physical, functional accounts, between subjective and objective perspectives, first person and third person accounts. Huxley (1866) stated the
* Tel.: #44 (0)1784 443516; fax: #44 (0)1784 434347; e-mail: [email protected] 0732—118X/99/$ — See front matter 1999 Elsevier Science Ltd. All rights reserved. PII: S 07 3 2— 1 18 X ( 98 ) 0 00 1 7— 8
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problem as that of ‘‘How it is that anything so remarkable as a state of consciousness comes about as a result of irritating nervous tissue is just as unaccountable as the appearance of Djinn when Aladdin rubbed his lamp.’’ Lockwood (1989) states it thus: ‘‘The most puzzling thing about consciousness, awareness, sentience is the fact that it exists. There is on the face of it absolutely nothing in the laws of physics and chemistry, as currently understood, that is capable of accounting for the extraordinary capacity of that lump of matter that we call the brain — to sustain ‘inner life’.’’ This age-old problem has been given many labels. Jackendoff (1987) speaks of the mind—mind problem, Flanagan (1991) of experiential and informational sensitivity and Block (1995) of phenomenal and access consciousness (a slightly different distinction). Currently fashionable are the ‘explanatory gap’, coined by Levine (1983) and the ‘hard question’: how to give a principled account of the connection between subjective experience and objective scientific accounts of behavioural and neurophysiological processes. Block (1994) outlines three attitudes to the explanatory gap: (1) The view that there is no gap — consciousness doesn’t exist in the sense intended so there is nothing for there to be a gap between, e.g. eliminative materialism (Churchland, 1983; Dennett, 1988; Rey, 1983) [Eliminativism]. (2) The view that there is an unclosable gap — there is a gap but the problem is insoluble. This exists in a variety of versions according to the reason given: (a) consciousness is transcendental rather than natural, so it is not explicable in scientific terms (e.g. White, 1991) [‘Transcendentalism’]; (b1) ‘awareness is an irreducible property of the activity of functionally entrained neuronal assemblies and therefore is amenable to no further explanation’ (Kinsbourne, 1993) [Irreducibility]; (b2) an a priori analysis of the phenomenon to be reduced (e.g. qualia) is required but cannot be given [Deflationist]; and (c) there are physical properties of the brain that explain consciousness but we cannot know them, so the solution to the problem is closed to us (McGinn, 1991) [New mysterianism]. (3) The view that there is a closable gap — there is a gap but the problem is soluble. Again this view exists in a number of forms: (a) currently we lack the scientific concepts but the problem may become soluble in the future (e.g. Flanagan, 1992; Nagel, 1974; Searle, 1992) [Naturalism]; and (b) the problem is not remarkable and is no different from other unsolved problems such as the physical or functional basis of liquidity, inheritance or computation [Reductionism].
2. Popper’s three worlds and attitudes to the explanatory gap My thesis is that Popper’s three worlds can be used as an intuition pump to reveal the insight that all three attitudes to the explanatory gap are true from different perspectives. Popper’s (Popper and Eccles, 1977) three worlds are: World 1, the world of physical objects which obey physical laws; World 2, the world of mental states and subjective experiences; and World 3, products of the human mind, abstract cultural objects, objective knowledge such as numbers, theories or books, which are governed by normative principles such as the rules of logic. Let us consider these as different realms, in the hope of avoiding the charge of ‘trialism’.
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Reflection on Popper’s World 1 of physical objects can be used to reveal the truth that, ontologically, there is only one world. This insight relies on the current prejudice that the physical world is ontologically basic — a prejudice which quantum mechanics shows to be misplaced, in that matter is just as puzzling as mind; indeed, it could be argued that it is the least knowable of the three worlds. I take it to refer to the Kantian noumena, ‘‘things-in-themselves — as they really are’’, whether we can know them or not. In this sense, mind—brain identity theory and Churchland’s eliminative materialism are correct. As Tukiainen (1995), a defender of the thesis, asks rhetorically, ‘‘How would an immaterial mind be any better situated to feel the qualia than a physical brain?’’ and goes on: ‘‘The broad picture is one where first-person and third-person ways of coming to know about events in our heads are ways of coming to know about one and the same events 2. They are the same objects under different descriptions.’’ From this perspective there is no gap. But this ‘no-nonsense materialism’ is unaware of the problems left unsolved. As Flanagan (1991) remarks: ‘‘If mental processes are identical to physical processes, how can it be that the true story of how my brain works will not capture what it is like to be me? The alleged mystery of consciousness has its source in biological facts which underwrite different kinds of epistemic access we have to brain facts on one hand and what it is like to be each of us, on the other.’’ (p. 342). Reflection on Popper’s World 2 forces us to acknowledge the reality of the mental aspect. It reveals the insight that, epistemically, dual aspect theory is true. This is a neo-Spinozistic view that subjective and objective are two different perspectives and, more particularly, that obscuring the distinction between them is to commit a Rylean category error. Epistemologically, there is an irresolvable duality, an unclosable gap. Headaches are not equivalent to dispositions to take aspirins. Blind neurophysiologists cannot experience colour vision, any more than male gynaecologists can experience childbirth. Reflection on Popper’s World 3 of cultural objects reveals the sense in which the gap is closable and the hard problem soluble: in the realm of scientific discourse. Here the task is to give a principled account of the relation between the phenomenal or subjective and the functional or objective. We can still isolate specific properties that subserve first person experience even if we can’t capture first person phenomenology third personally (Flanagan, 1991). It is important to be clear about what is and what is not being done here. Scientific theory can only relate inferred entities or concepts, not actual experience itself. A scientific theory of conscious experience won’t itself experience in the same way as a chemical theory is not itself expected to fizz (Boden, 1979). Flanagan believes that it will be possible to give a naturalistic explanation of our inability to capture the phenomenology of what it is like to be each one of us from the objective point of view. At the end of this article I shall indicate that this has already been achieved.
3. Closing the gap Is closing the gap a philosophical or a scientific problem? I believe that it is a philosophical task to map out and clarify which problems can and which cannot be
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solved, in the way I have attempted above; and, further, to specify what would count as a solution to the soluble problem. What requirements have to be met? On the other hand, I agree with Zeki (personal communication, 1996) that one good experiment is worth a thousand fruitless speculations, and with Lockwood (1989) that new ways of thinking are likely to be inspired by reflecting on empirical discoveries. It is generally agreed that closure of the gap, or the solution of the hard problem, must involve more than ‘brute correlation’. A principled account of the relation between phenomenal and functional features must be provided, perhaps taking the form of some kind of theoretical isomorphism. Nagel (1993) demands that the explanation be ‘transparent’. Opinion is divided as to whether it is just a matter of providing more information of the same kind or whether a paradigmatic revolution has to occur. It may be a matter of degree — like explanation — simply a matter of providing more information of various kinds. This ambiguity is apparent in Gray’s (1995) target article, where he is unsure of whether or not he has moved beyond brute correlation and if so how or how far. Are people seeking a holy grail, a magic formula, a philosopher’s stone? Is Kinsbourne (1995) right when he asserts that ‘‘To call for a paradigm shift to explain consciousness may be overkill’’ (p. 687)? On the other hand, Lockwood (1989) believes that it is not just a matter of more information of the same kind as we have already; rather, a drastic revision of our customary way of looking at the world is required. The following phenomenal features of consciousness need to be accounted for: (1) Unity — the belongingness of diverse items within the perceptual field both to the observer and to each other, the simultaneous integration of items both within and between different sense modalities. An answer is required to Schro¨dinger’s question: how can a single mind arise out of a population of communicating individuals? Or to what is now known as the binding problem: how are different qualities, known to be analysed in different regions, united in awareness? Different attributes are analysed in spatially disparate areas of the cortex, both inter-modally, e.g. the coincident qualia which result in the wasp being seen, heard and felt as being in one and the same place; and intra-modally, e.g. Zeki’s (1993) work establishing different areas for the analysis of form, colour and motion in vision. The functional and anatomical separability of these is demonstrated by specific visual agnosias: damage of one area leads to loss of one attribute, e.g. damage to area V4 results in the reduction of colour vision to black and white. What has to be accounted for is the fact that we never have the experience of bad colour printing, where form and colour don’t quite map onto each other. (2) Privacy — the fact that consciousness is confined to the individual. (3) The perception of time, both its apparent continuity and discreteness. Psychological moments have a certain thickness or duration and overlap each other. Apparent time is ‘smeared’ in relation to real time. We can perceive change and motion. (4) The contents of consciousness.
4. From brute correlation to transparency Much interest has centred on the 40 Hz oscillations associated with regions of the brain involved with conscious attention (Crick and Koch, 1990; Crick, 1994; Eckhorn
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et al., 1988; Gray and Singer, 1989) For example, Gray and Singer (1989) showed that in areas 17 and 18 of the cat visual cortex the firing probability of neurons, in response to the presentation of optimally aligned bars within their receptive field, oscillates with a peak frequency of near 40 Hz. Groups of adjacent cortical neurons, when activated appropriately, engage in cooperative interactions as postulated on theoretical grounds, for example, by Edelman (1978). These interactions lead to coherent and periodic patterns of activity, suggesting that the phase of the oscillatory response may be used as a further dimension of coding in addition to the amplitude and duration of the response. One role for this temporal code would be to enable columns of cells in different parts of the cortex, representing different parts of the visual field, to synchronize their respective activity patterns. Thus, the oscillatory responses may provide a general mechanism by which activity patterns in spatially separate regions of the cortex are temporally coordinated. However, the account in terms of 40 Hz is generally thought not to be principled, and in any case is too slow for unification. Mere synchronicity or simultaneity and coherence do not provide a sufficient explanation of unity. ‘‘We may still ask how the mere synchronicity and simultaneity of the oscillations throughout the [corticocollicular neuronal] group give rise to the unitary experienced object.’’ (Valentine, 1995, p. 42; italics mine). No mechanism is given for translating synchronous oscillations into unified experiences. ‘‘As phenomenologists, we desire to know how it is that qualities analyzed in spatially discrete tissues are united in awareness. Surely, mere synchronicity will not provide an explanation of that.’’ (Valentine, 1995, p. 45; italics mine). Other examples of crude parallels to phenomenal features in functional features are distributed processing and Pribram’s idea of global (essentially quantum) largescale coherent ‘holographic’ activity in the brain. However, as Dennett (1984) pointed out, some of the attraction of holism is that it is ‘organic and fuzzy and warm and cuddly and mysterious’. Two neuropsychological theories seek to account for many of the phenomenological features of conscious experiences by postulating specific neural and/or psychological functions that might give rise to them. O’Keefe’s (1985) theory that consciousness is to be identified with activation of the theta system which organises neocortical and entorhinal inputs into the hippocampus, and which synchronises all three structures for the construction, correction and manipulation of maps of the environment, is based on observed parallels between introspectively derived characteristics of consciousness and the anatomy and physiology of the rat septo-hippocampal system. Unity or holism is accounted for by distributed representation; the distinctions between the focus and fringe of attention, and between external and internal modes of controlling consciousness, by the contrast between mismatch signals generated by the hippocampus and normal activation direct from the brain stem; the distinction between conscious and nonconscious behaviour by that between flexible and rigid control of the motor system, as in place versus non-place learning; multi-modality by the integration of modality-specific sensory input from the neo-cortex; and long-term narrative memory by the role of the hippocampus in memory. Gray’s (1995) similar but independently developed neuropsychological hypothesis is that the contents of consciousness consist of outputs of a (subicular) comparator
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system that, on a moment-to-basis, compares the current state of the organism’s perceptual world with a predicted state, together with feedback from the comparator to those sets of neurons in perceptual systems which have just provided input to the comparator in respect of the current process of comparison. He claims that his hypothesis goes beyond brute correlation but falls far short of Nagel’s standard of transparency. An empirical objection to both these theories is that destruction of the hippocampus does not abolish consciousness. Most of the interest in trying to provide physical accounts of phenomenal features of consciousness has occurred in physics. The relevance of quantum physical accounts for consciousness is controversial. Although the relation of accounts at the neurophysiological and physical levels to accounts at the psychological level remains problematical, it behoves philosophers of mind to become cognisant with quantum physics. As early as 1931, Bohr speculated about the role of quantum effects in the brain and Haldane (1963) explored exciting implications for temporal phenomena. Many have canvassed the notion that a state of the brain exhibiting quantum coherence might be the physical basis of consciousness. The most popular hypothesis has been that Bose—Einstein condensation may provide the unitary sense of self (Lockwood, 1989; Marshall, 1989; Zohar, 1990; Zohar and Marshall, 1994). In 1970, Fro¨lich showed that, in systems of vibrating electrically charged molecules (dipoles), beyond a certain threshold when incoming energy reaches a critical value, any additional energy pumped into the system causes molecules to vibrate in unison, producing so-called Bose—Einstein condensation, the most ordered form of condensed phase possible. There is large-scale quantum synchronicity, quanta becoming coherent over macroscopic regions. Parts become a whole in that they lose their individuality. Wave functions overlap, resulting in indeterminate spatial location. Marshall (1989) was the first person to put forward the idea that Bose condensation in such pumped phonon systems might be the basis of mental states and processes. He argued that the collective and holistic character of Bose-condensed oscillatory states might be the physical basis of consciousness, suggesting that information might be encoded by appropriately adjusting amplitudes (possibly the physical basis of intensity of sensation) and relative phase (possibly the physical basis of quality of sensation). These ideas were popularised and embedded in a much larger panpsychist theory by Zohar (1990). More recently, Penrose (1994) has also favoured the view that a state of the brain exhibiting quantum coherence might be the physical basis of consciousness (specifying microtubules as the locus of the effect — a dubious hypothesis), again suggesting that this could account for the global nature of consciousness: ‘‘The unity of a single mind can arise2 only if there is some form of quantum coherence extending across at least an appreciable part of the entire brain.’’ (Penrose, 1994, p. 372). In his case this is part of a wider theory concerning the interplay between quantum and classical levels of activity. Lockwood (1989) summarises the case in favour thus: ‘‘Fro¨lich’s Bose-condensed oscillatory states certainly seem to fit the bill. They are indeed global, with respect to the individual oscillators. Within such a system, information would be non-localised, transcending the states of individual oscillators, in a sense even stronger than that in which information could be said to be ‘distributed’ within a neural network or
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a hologram. In phonon terminology, the coherence of these states means that the associated phonons have sharply defined momenta, and hence, by the uncertainty principle, highly indeterminate positions; the phonons, or more strictly, their position wave function, are spread out over the area occupied by the coherent state... They lend themselves to coherent superposition, with constructive and destructive interference in just the way that is required of computer memory states.’’ (p. 259). It must be acknowledged that this theory is at present highly speculative. It is not known for certain whether mechanisms of the kind Fro¨lich proposed exist at all, let alone in the brain. On the other hand, despite what Grush and Churchland (1995) refer to as ‘‘the rather breathtaking flimsiness of the quantum-consciousness connection’, the very existence of a viable quantum mechanical model of consciousness is already pregnant with far reaching philosophical implications (Zohar, 1990). Furthermore, the convergence of different approaches lends credibility to the hypothesis. Five years before the publication of Marshall’s article, a little known article by Valentine (1982; see also, Valentine, 1995) pursued the attempt to account for the phenomenal features of consciousness by searching for parallel physical features. In his view, Fermi—Dirac statistics give a stronger sense of indistinguishability than do Bose—Einstein. In the former case the particles are not only indistinguishable but non-individuated. Two indistinguishable Bose—Einstein particles can be in the same state; however, in the Fermi—Dirac case, there is a strong sense in which there can be said to be only one particle. Thus, the physical basis of consciousness is postulated to lie in electrons rather than photons. It is argued that the unity of consciousness may be accounted for by the fact that particular electrons in a bound state are indistinguishable and non-localisable. The privacy of consciousness could be accounted for by the fact that electronic events within separate quantum systems are independent of each other, since the wave function comes to zero at the system’s boundaries, thus providing a solution to Flanagan’s problem, of providing a naturalistic explanation of our inability to capture the phenomenology of what it is like to be each one of us from the objective point of view. In agreement with Gray (1995), it is suggested that quantisation is physics’s way of discretising time. The brain appears to be a system of variable electronic interconnexions which can only be altered quantally. Thus events occur in discrete packets and extend in time. This could account for the ‘‘thickness’’ or duration and overlapping of psychological moments.
5. Summary and conclusions Popper’s three worlds were used as an intuition pump to reveal the senses in which the hard problem can and cannot be solved. Ontologically, there is no gap and hence no problem to be solved. Epistemically, there is an unclosable gap, an irresolvable duality and hence an insoluble problem. From the point of view of scientific theory, there is a soluble problem, that of providing a principled account of the relation between phenomenal features of consciousness and functional accounts in terms of behaviour, neurophysiology and physics. Various attempted solutions were reviewed. Those constituting mere brute correlations were rejected in favour of those offering
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parallels with phenomenal features of consciousness sufficiently powerful to provide a transparent account. It is concluded that examples of the latter are currently in existence.
Acknowledgement This paper is based on an address to the History & Philosophy Section of the British Psychological Society, an excerpted version of which was published in M.C. Chung (Ed.) Psychological concepts from philosophical and historical perspectives. Leicester: British Psychological Society, 1997.
References Block, N. (1994). Consciousness. In S. Guttenplan (Ed.), Companion to the philosophy of mind (pp. 210—218). Oxford: Oxford University Press. Block, N. (1995). On a confusion about a function of consciousness. Behavioral & Brain Sciences, 18, 227—287. Boden, M. (1979). The computational metaphor in psychology. In N. Bolton (Ed.) Philosophical problems in psychology, (pp. 111—132). London: Methuen. Churchland, P.S. (1983). Consciousness: the transmutation of a concept. Pacific Philosophical Quarterly, 64, 80—93. Crick, F. (1994). ¹he astonishing hypothesis: ¹he scientific search for the soul. Cambridge: Cambridge University Press. Crick, F., & Koch, C. (1990). Towards a biological theory of consciousness. Seminars in the Neurosciences, 2, 263—75. Dennett, D.C. (1984). Computer models and the mind — a view from the East Pole. ¹imes ¸iterary Supplement, 14 December, (p. 1453). Dennett, D.C. (1988). Quining qualia. In A. Marcel, & E. Bisiach (Eds.) Consciousness in contemporary society (pp. 42—77). Oxford: Oxford University Press. Eckhorn, R., Bauer, R., Jordan, W., Brosch, M., Kruse, W., Munk, M., & Reitbock, H.J. (1988). Coherent oscillations: A mechanism of feature linking in the visual cortex. Biological Cybernetics, 60, 121—30. Edelman, G.M. (1978). ¹he mindful brain. Cambridge, MA: MIT Press. Flanagan, O. (1991). ¹he science of mind. (2nd edn). Cambridge, MA: MIT Press. Flanagan, O. (1992). Consciousness reconsidered. Cambridge, MA: MIT Press. Fro¨lich, H. (1968). Long-range coherence and energy storage in biological systems. International Journal of Quanta Chemistry, 2, 641—49. Gray, C.M., & Singer, W. (1989). Stimulus-specific neuronal oscillations in orientation columns of cat visual cortex. Proceedings of the National Academy of Science, ºSA, 86, 1698—1702. Gray, J.A. (1995). The contents of consciousness: A neuropsychological conjecture. Behavioral and Brain Sciences, 18, 659—722. Grush, R., & Churchland, P.S. (1995). Gaps in Penrose’s toiling. Journal of Consciousness Studies, 2, 10—29. Haldane, J.B.S. (1963). Life and mind as physical realities, Penguin Science Survey B, 224—238. Huxley, T.H. (1866). ¸essons in elementary physiology, viii. London: Macmillan. Jackendoff, R. (1987). Consciousness and the computational mind. Cambridge, MA: MIT Press. Kinsbourne, M. (1993). Integrated cortical field model of consciousness In Experimental studies of consciousness, CIBA Symposium (Vol. 174). Chichester: Wiley. Kinsbourne, M. (1995). Septo-hippocampal comparator: Consciousness generator or attention feedback loop? Behavioral and Brain Sciences, 18, 687—78.
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Levine, J. (1983). Materialism and qualia: The explanatory gap. Pacific Philosophical Quarterly, 64, 354—61. Lockwood, M. (1989). Mind, brain & the quantum: ¹he compound ‘I’. Oxford: Blackwell. Marshall, I.N. (1989). Consciousness and Bose—Einstein condensates. New Ideas in Psychology, 7, 73—83. McGinn, C. (1991). ¹he problem of consciousness. Oxford: Basil Blackwell. Nagel, T. (1974). What is it like to be a bat? Philosophical Review, 83, 435—50. Nagel, T. (1993). What is the mind-body problem? In Experimental studies of consciousness, CIBA Symposium (Vol. 174). Chichester: Wiley. O’Keefe, J. (1985). Is consciousness the gateway to the hippocampal map? In D. Oakley (Ed.), Brain and mind. (pp. 59—98). London: Methuen. Penrose, R. (1994). Shadows of the mind. Oxford: Oxford University Press. Popper, K.R., & Eccles, J.C. (1977). ¹he self and its brain. Berlin: Springer-Verlag. Rey, G. (1983). A reason for doubting the existence of consciousness. In R. Davidson, G. Schwartz, & D. Shapiro (Eds.), Consciousness and self-regulation (pp. 1—39). New York: Plenum. Searle, J. (1992). ¹he Rediscovery of Mind. Cambridge, MA: MIT Press. Tukiainen, A. (1995). Is ‘‘subjectivity of consciousness’’ a problem to physicalism? In P. Pylkka¨nen, & P. Pylkko¨ (Eds.), New directions in cognitive science (pp. 168-77). Helsinki: Finnish Artificial Intelligence Society. Valentine, J.D. (1982). Towards a physics of consciousness. Psychoenergetics 4, 257—74. Valentine, J. (1995). Physical implications of coincident qualia. In Consciousness at the crossroads of philosophy and cognitive science (pp. 39—48). Thorverton: Imprint Academic. White, S.L. (1991). Transcendentalism and its discontents. In ¹he unity of the self (pp. 103—132). Cambridge, MA: MIT Press. Zeki, S. (1993). A vision of the brain. Oxford: Blackwell. Zohar, D. (1990). ¹he quantum self. London: Bloomsbury. Zohar, D., & Marshall, I.N. (1994). ¹he quantum society: Mind, physics and a new social vision. London: Bloomsbury.
Popper’s three worlds and attitudes to the explanatory gap Elizabeth Valentine* Department of Psychology, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
Abstract The thesis is explored that Popper’s three worlds may be used as an intuition pump to reveal the insight that all three attitudes to the explanatory gap (that there is no gap, an unclosable gap, or a closable gap) are true from different perspectives. Ontologically, there is only one world and no gap. Epistemically, there is an irresolvable duality, an unclosable gap. From the point of view of scientific theory, there is a soluble problem, that of providing a principled account of the relation between phenomenal features of consciousness and functional accounts in terms of behaviour, neurophysiology and physics. Requirements for filling the gap are examined in more detail, and attempts to fill the gap are discussed. It is argued that, on current knowledge, it appears that only at the level of sub-atomic physics can parallels with phenomenal features of consciousness be found that are sufficiently powerful to provide a transparent account. 1999 Elsevier Science Ltd. All rights reserved.
Since, therefore, the substance of the mind has been found to be extraordinarily mobile, it must consist of particles exceptionally small and smooth and round. - Lucretius.
1. The explanatory gap The central problem in the philosophy of mind, which has attracted more attention than any other, is that of the relation between phenomenal and functional consciousness, the mind—body or mind—brain problem, i.e., the relation between phenomenal experience (qualia, what it is like to be... a phrase due originally to Brian Farrell rather than Thomas Nagel) and physical, functional accounts, between subjective and objective perspectives, first person and third person accounts. Huxley (1866) stated the
* Tel.: #44 (0)1784 443516; fax: #44 (0)1784 434347; e-mail: [email protected] 0732—118X/99/$ — See front matter 1999 Elsevier Science Ltd. All rights reserved. PII: S 07 3 2— 1 18 X ( 98 ) 0 00 1 7— 8
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E. Valentine/New Ideas in Psychology 17 (1999) 31—39
problem as that of ‘‘How it is that anything so remarkable as a state of consciousness comes about as a result of irritating nervous tissue is just as unaccountable as the appearance of Djinn when Aladdin rubbed his lamp.’’ Lockwood (1989) states it thus: ‘‘The most puzzling thing about consciousness, awareness, sentience is the fact that it exists. There is on the face of it absolutely nothing in the laws of physics and chemistry, as currently understood, that is capable of accounting for the extraordinary capacity of that lump of matter that we call the brain — to sustain ‘inner life’.’’ This age-old problem has been given many labels. Jackendoff (1987) speaks of the mind—mind problem, Flanagan (1991) of experiential and informational sensitivity and Block (1995) of phenomenal and access consciousness (a slightly different distinction). Currently fashionable are the ‘explanatory gap’, coined by Levine (1983) and the ‘hard question’: how to give a principled account of the connection between subjective experience and objective scientific accounts of behavioural and neurophysiological processes. Block (1994) outlines three attitudes to the explanatory gap: (1) The view that there is no gap — consciousness doesn’t exist in the sense intended so there is nothing for there to be a gap between, e.g. eliminative materialism (Churchland, 1983; Dennett, 1988; Rey, 1983) [Eliminativism]. (2) The view that there is an unclosable gap — there is a gap but the problem is insoluble. This exists in a variety of versions according to the reason given: (a) consciousness is transcendental rather than natural, so it is not explicable in scientific terms (e.g. White, 1991) [‘Transcendentalism’]; (b1) ‘awareness is an irreducible property of the activity of functionally entrained neuronal assemblies and therefore is amenable to no further explanation’ (Kinsbourne, 1993) [Irreducibility]; (b2) an a priori analysis of the phenomenon to be reduced (e.g. qualia) is required but cannot be given [Deflationist]; and (c) there are physical properties of the brain that explain consciousness but we cannot know them, so the solution to the problem is closed to us (McGinn, 1991) [New mysterianism]. (3) The view that there is a closable gap — there is a gap but the problem is soluble. Again this view exists in a number of forms: (a) currently we lack the scientific concepts but the problem may become soluble in the future (e.g. Flanagan, 1992; Nagel, 1974; Searle, 1992) [Naturalism]; and (b) the problem is not remarkable and is no different from other unsolved problems such as the physical or functional basis of liquidity, inheritance or computation [Reductionism].
2. Popper’s three worlds and attitudes to the explanatory gap My thesis is that Popper’s three worlds can be used as an intuition pump to reveal the insight that all three attitudes to the explanatory gap are true from different perspectives. Popper’s (Popper and Eccles, 1977) three worlds are: World 1, the world of physical objects which obey physical laws; World 2, the world of mental states and subjective experiences; and World 3, products of the human mind, abstract cultural objects, objective knowledge such as numbers, theories or books, which are governed by normative principles such as the rules of logic. Let us consider these as different realms, in the hope of avoiding the charge of ‘trialism’.
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Reflection on Popper’s World 1 of physical objects can be used to reveal the truth that, ontologically, there is only one world. This insight relies on the current prejudice that the physical world is ontologically basic — a prejudice which quantum mechanics shows to be misplaced, in that matter is just as puzzling as mind; indeed, it could be argued that it is the least knowable of the three worlds. I take it to refer to the Kantian noumena, ‘‘things-in-themselves — as they really are’’, whether we can know them or not. In this sense, mind—brain identity theory and Churchland’s eliminative materialism are correct. As Tukiainen (1995), a defender of the thesis, asks rhetorically, ‘‘How would an immaterial mind be any better situated to feel the qualia than a physical brain?’’ and goes on: ‘‘The broad picture is one where first-person and third-person ways of coming to know about events in our heads are ways of coming to know about one and the same events 2. They are the same objects under different descriptions.’’ From this perspective there is no gap. But this ‘no-nonsense materialism’ is unaware of the problems left unsolved. As Flanagan (1991) remarks: ‘‘If mental processes are identical to physical processes, how can it be that the true story of how my brain works will not capture what it is like to be me? The alleged mystery of consciousness has its source in biological facts which underwrite different kinds of epistemic access we have to brain facts on one hand and what it is like to be each of us, on the other.’’ (p. 342). Reflection on Popper’s World 2 forces us to acknowledge the reality of the mental aspect. It reveals the insight that, epistemically, dual aspect theory is true. This is a neo-Spinozistic view that subjective and objective are two different perspectives and, more particularly, that obscuring the distinction between them is to commit a Rylean category error. Epistemologically, there is an irresolvable duality, an unclosable gap. Headaches are not equivalent to dispositions to take aspirins. Blind neurophysiologists cannot experience colour vision, any more than male gynaecologists can experience childbirth. Reflection on Popper’s World 3 of cultural objects reveals the sense in which the gap is closable and the hard problem soluble: in the realm of scientific discourse. Here the task is to give a principled account of the relation between the phenomenal or subjective and the functional or objective. We can still isolate specific properties that subserve first person experience even if we can’t capture first person phenomenology third personally (Flanagan, 1991). It is important to be clear about what is and what is not being done here. Scientific theory can only relate inferred entities or concepts, not actual experience itself. A scientific theory of conscious experience won’t itself experience in the same way as a chemical theory is not itself expected to fizz (Boden, 1979). Flanagan believes that it will be possible to give a naturalistic explanation of our inability to capture the phenomenology of what it is like to be each one of us from the objective point of view. At the end of this article I shall indicate that this has already been achieved.
3. Closing the gap Is closing the gap a philosophical or a scientific problem? I believe that it is a philosophical task to map out and clarify which problems can and which cannot be
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solved, in the way I have attempted above; and, further, to specify what would count as a solution to the soluble problem. What requirements have to be met? On the other hand, I agree with Zeki (personal communication, 1996) that one good experiment is worth a thousand fruitless speculations, and with Lockwood (1989) that new ways of thinking are likely to be inspired by reflecting on empirical discoveries. It is generally agreed that closure of the gap, or the solution of the hard problem, must involve more than ‘brute correlation’. A principled account of the relation between phenomenal and functional features must be provided, perhaps taking the form of some kind of theoretical isomorphism. Nagel (1993) demands that the explanation be ‘transparent’. Opinion is divided as to whether it is just a matter of providing more information of the same kind or whether a paradigmatic revolution has to occur. It may be a matter of degree — like explanation — simply a matter of providing more information of various kinds. This ambiguity is apparent in Gray’s (1995) target article, where he is unsure of whether or not he has moved beyond brute correlation and if so how or how far. Are people seeking a holy grail, a magic formula, a philosopher’s stone? Is Kinsbourne (1995) right when he asserts that ‘‘To call for a paradigm shift to explain consciousness may be overkill’’ (p. 687)? On the other hand, Lockwood (1989) believes that it is not just a matter of more information of the same kind as we have already; rather, a drastic revision of our customary way of looking at the world is required. The following phenomenal features of consciousness need to be accounted for: (1) Unity — the belongingness of diverse items within the perceptual field both to the observer and to each other, the simultaneous integration of items both within and between different sense modalities. An answer is required to Schro¨dinger’s question: how can a single mind arise out of a population of communicating individuals? Or to what is now known as the binding problem: how are different qualities, known to be analysed in different regions, united in awareness? Different attributes are analysed in spatially disparate areas of the cortex, both inter-modally, e.g. the coincident qualia which result in the wasp being seen, heard and felt as being in one and the same place; and intra-modally, e.g. Zeki’s (1993) work establishing different areas for the analysis of form, colour and motion in vision. The functional and anatomical separability of these is demonstrated by specific visual agnosias: damage of one area leads to loss of one attribute, e.g. damage to area V4 results in the reduction of colour vision to black and white. What has to be accounted for is the fact that we never have the experience of bad colour printing, where form and colour don’t quite map onto each other. (2) Privacy — the fact that consciousness is confined to the individual. (3) The perception of time, both its apparent continuity and discreteness. Psychological moments have a certain thickness or duration and overlap each other. Apparent time is ‘smeared’ in relation to real time. We can perceive change and motion. (4) The contents of consciousness.
4. From brute correlation to transparency Much interest has centred on the 40 Hz oscillations associated with regions of the brain involved with conscious attention (Crick and Koch, 1990; Crick, 1994; Eckhorn
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et al., 1988; Gray and Singer, 1989) For example, Gray and Singer (1989) showed that in areas 17 and 18 of the cat visual cortex the firing probability of neurons, in response to the presentation of optimally aligned bars within their receptive field, oscillates with a peak frequency of near 40 Hz. Groups of adjacent cortical neurons, when activated appropriately, engage in cooperative interactions as postulated on theoretical grounds, for example, by Edelman (1978). These interactions lead to coherent and periodic patterns of activity, suggesting that the phase of the oscillatory response may be used as a further dimension of coding in addition to the amplitude and duration of the response. One role for this temporal code would be to enable columns of cells in different parts of the cortex, representing different parts of the visual field, to synchronize their respective activity patterns. Thus, the oscillatory responses may provide a general mechanism by which activity patterns in spatially separate regions of the cortex are temporally coordinated. However, the account in terms of 40 Hz is generally thought not to be principled, and in any case is too slow for unification. Mere synchronicity or simultaneity and coherence do not provide a sufficient explanation of unity. ‘‘We may still ask how the mere synchronicity and simultaneity of the oscillations throughout the [corticocollicular neuronal] group give rise to the unitary experienced object.’’ (Valentine, 1995, p. 42; italics mine). No mechanism is given for translating synchronous oscillations into unified experiences. ‘‘As phenomenologists, we desire to know how it is that qualities analyzed in spatially discrete tissues are united in awareness. Surely, mere synchronicity will not provide an explanation of that.’’ (Valentine, 1995, p. 45; italics mine). Other examples of crude parallels to phenomenal features in functional features are distributed processing and Pribram’s idea of global (essentially quantum) largescale coherent ‘holographic’ activity in the brain. However, as Dennett (1984) pointed out, some of the attraction of holism is that it is ‘organic and fuzzy and warm and cuddly and mysterious’. Two neuropsychological theories seek to account for many of the phenomenological features of conscious experiences by postulating specific neural and/or psychological functions that might give rise to them. O’Keefe’s (1985) theory that consciousness is to be identified with activation of the theta system which organises neocortical and entorhinal inputs into the hippocampus, and which synchronises all three structures for the construction, correction and manipulation of maps of the environment, is based on observed parallels between introspectively derived characteristics of consciousness and the anatomy and physiology of the rat septo-hippocampal system. Unity or holism is accounted for by distributed representation; the distinctions between the focus and fringe of attention, and between external and internal modes of controlling consciousness, by the contrast between mismatch signals generated by the hippocampus and normal activation direct from the brain stem; the distinction between conscious and nonconscious behaviour by that between flexible and rigid control of the motor system, as in place versus non-place learning; multi-modality by the integration of modality-specific sensory input from the neo-cortex; and long-term narrative memory by the role of the hippocampus in memory. Gray’s (1995) similar but independently developed neuropsychological hypothesis is that the contents of consciousness consist of outputs of a (subicular) comparator
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system that, on a moment-to-basis, compares the current state of the organism’s perceptual world with a predicted state, together with feedback from the comparator to those sets of neurons in perceptual systems which have just provided input to the comparator in respect of the current process of comparison. He claims that his hypothesis goes beyond brute correlation but falls far short of Nagel’s standard of transparency. An empirical objection to both these theories is that destruction of the hippocampus does not abolish consciousness. Most of the interest in trying to provide physical accounts of phenomenal features of consciousness has occurred in physics. The relevance of quantum physical accounts for consciousness is controversial. Although the relation of accounts at the neurophysiological and physical levels to accounts at the psychological level remains problematical, it behoves philosophers of mind to become cognisant with quantum physics. As early as 1931, Bohr speculated about the role of quantum effects in the brain and Haldane (1963) explored exciting implications for temporal phenomena. Many have canvassed the notion that a state of the brain exhibiting quantum coherence might be the physical basis of consciousness. The most popular hypothesis has been that Bose—Einstein condensation may provide the unitary sense of self (Lockwood, 1989; Marshall, 1989; Zohar, 1990; Zohar and Marshall, 1994). In 1970, Fro¨lich showed that, in systems of vibrating electrically charged molecules (dipoles), beyond a certain threshold when incoming energy reaches a critical value, any additional energy pumped into the system causes molecules to vibrate in unison, producing so-called Bose—Einstein condensation, the most ordered form of condensed phase possible. There is large-scale quantum synchronicity, quanta becoming coherent over macroscopic regions. Parts become a whole in that they lose their individuality. Wave functions overlap, resulting in indeterminate spatial location. Marshall (1989) was the first person to put forward the idea that Bose condensation in such pumped phonon systems might be the basis of mental states and processes. He argued that the collective and holistic character of Bose-condensed oscillatory states might be the physical basis of consciousness, suggesting that information might be encoded by appropriately adjusting amplitudes (possibly the physical basis of intensity of sensation) and relative phase (possibly the physical basis of quality of sensation). These ideas were popularised and embedded in a much larger panpsychist theory by Zohar (1990). More recently, Penrose (1994) has also favoured the view that a state of the brain exhibiting quantum coherence might be the physical basis of consciousness (specifying microtubules as the locus of the effect — a dubious hypothesis), again suggesting that this could account for the global nature of consciousness: ‘‘The unity of a single mind can arise2 only if there is some form of quantum coherence extending across at least an appreciable part of the entire brain.’’ (Penrose, 1994, p. 372). In his case this is part of a wider theory concerning the interplay between quantum and classical levels of activity. Lockwood (1989) summarises the case in favour thus: ‘‘Fro¨lich’s Bose-condensed oscillatory states certainly seem to fit the bill. They are indeed global, with respect to the individual oscillators. Within such a system, information would be non-localised, transcending the states of individual oscillators, in a sense even stronger than that in which information could be said to be ‘distributed’ within a neural network or
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a hologram. In phonon terminology, the coherence of these states means that the associated phonons have sharply defined momenta, and hence, by the uncertainty principle, highly indeterminate positions; the phonons, or more strictly, their position wave function, are spread out over the area occupied by the coherent state... They lend themselves to coherent superposition, with constructive and destructive interference in just the way that is required of computer memory states.’’ (p. 259). It must be acknowledged that this theory is at present highly speculative. It is not known for certain whether mechanisms of the kind Fro¨lich proposed exist at all, let alone in the brain. On the other hand, despite what Grush and Churchland (1995) refer to as ‘‘the rather breathtaking flimsiness of the quantum-consciousness connection’, the very existence of a viable quantum mechanical model of consciousness is already pregnant with far reaching philosophical implications (Zohar, 1990). Furthermore, the convergence of different approaches lends credibility to the hypothesis. Five years before the publication of Marshall’s article, a little known article by Valentine (1982; see also, Valentine, 1995) pursued the attempt to account for the phenomenal features of consciousness by searching for parallel physical features. In his view, Fermi—Dirac statistics give a stronger sense of indistinguishability than do Bose—Einstein. In the former case the particles are not only indistinguishable but non-individuated. Two indistinguishable Bose—Einstein particles can be in the same state; however, in the Fermi—Dirac case, there is a strong sense in which there can be said to be only one particle. Thus, the physical basis of consciousness is postulated to lie in electrons rather than photons. It is argued that the unity of consciousness may be accounted for by the fact that particular electrons in a bound state are indistinguishable and non-localisable. The privacy of consciousness could be accounted for by the fact that electronic events within separate quantum systems are independent of each other, since the wave function comes to zero at the system’s boundaries, thus providing a solution to Flanagan’s problem, of providing a naturalistic explanation of our inability to capture the phenomenology of what it is like to be each one of us from the objective point of view. In agreement with Gray (1995), it is suggested that quantisation is physics’s way of discretising time. The brain appears to be a system of variable electronic interconnexions which can only be altered quantally. Thus events occur in discrete packets and extend in time. This could account for the ‘‘thickness’’ or duration and overlapping of psychological moments.
5. Summary and conclusions Popper’s three worlds were used as an intuition pump to reveal the senses in which the hard problem can and cannot be solved. Ontologically, there is no gap and hence no problem to be solved. Epistemically, there is an unclosable gap, an irresolvable duality and hence an insoluble problem. From the point of view of scientific theory, there is a soluble problem, that of providing a principled account of the relation between phenomenal features of consciousness and functional accounts in terms of behaviour, neurophysiology and physics. Various attempted solutions were reviewed. Those constituting mere brute correlations were rejected in favour of those offering
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parallels with phenomenal features of consciousness sufficiently powerful to provide a transparent account. It is concluded that examples of the latter are currently in existence.
Acknowledgement This paper is based on an address to the History & Philosophy Section of the British Psychological Society, an excerpted version of which was published in M.C. Chung (Ed.) Psychological concepts from philosophical and historical perspectives. Leicester: British Psychological Society, 1997.
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